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can someone give me a desciption of the dreaded rust

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#1 coyote



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Posted 22 May 2008 - 01:21 AM

I never heard of this rust problem till today so i checked my blocking filter and noticed a red ring on the outer edge of the inner end of the blocking filter.

#2 Larry Alvarez

Larry Alvarez

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Posted 22 May 2008 - 05:12 AM

The rust problem affects what I believe is called the ITF filter on the blocking filter.  It is the turquoise colored filter in the front of the blocking filter.  This filter is made up of two flat glass plates that have a metallic coating in the center.  Typically they are coated around the outer edge with a material to keep moisture out because they are suseptible to it and typically tend to rust from the outside in.  It looks sort of like the Helix nebula to me.

From past conversations with Coronado and Meade the scope is still safe to use and in most cases you will see a drop in the details you can see when this happens but the scope is still safe to use.  Getting it replaced is a simple matter of calling the Meade service number and speaking with a customer service person.  If your scope is under warranty I believe they only charge you the shipping costs for the BF.  The Meade number is 1-800-626-3233. 

I have had this happen to me a couple times and now I store my blocking filters in a small tupperware container with a couple packs of silica when the scope is not in use.  Since my were fixed a few years ago not one of the new ones has rusted but I am not storing them in an air tight case as mentioned before when I do not use them.  From what I know about the filters, the front etalon filter is not suseptible to this issue so it should last a lifetime but the material in the blocking filter diagonal is.  The very first PST telescopes made had their front objective coated with this same material and they also went bad after a short time until Meade fixed them with new optical lenses.  I am not sure they have a permanent fix for this issue but the replacement takes about 2 weeks after they received the blocking filter. 

Clear Skyz, LA

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